Effect of substituents in benzoxazole derivatives of biphenyl on the optical properties and photostability of their thin films

We have studied the characteristic features of the luminescence of thin films, formed by deposition from solutions and thermal vacuum deposition (TVD), of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2-fluorobiphenyl (BPh-1) and 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2,2′-difluorobiphenyl (BPh-2). We have established that fluorine atoms in the biphenyl moiety of the benzoxasole derivatives significantly improve the stability of the TVD films relative to oxidative aging compared with hexyloxy substituents. Irradiation with UV light stimulates quenching of luminescence and structuring of the TVD film of the difluoro-substituted derivative.